The demand for highly efficient energy storage and heat transfer encompasses a broad range of technologies involving any form of energy creation, storage and usage. In an age of increasing heat fluxes and power loads in applications as diverse as medical equipment, power electronics, renewable energy, and transportation, liquid cooling systems are necessary to enhance heat dissipation, improve energy efficiency, and lengthen devices lifetime. To satisfy these increasing thermal management needs, the heat transfer efficiency of conventional fluids must be improved. For example, there is a significant effort to develop and deploy viable renewable energy technologies. In this regard, for example, solar energy is one of the promising options. However, current costs to produce electricity using solar technologies, such as Concentrated Solar Power (“CSP”), are not cost competitive as compared to the traditional energy generation technologies based on fossil fuels and nuclear. Several strategies have been proposed to increase the overall efficiencies and reduce costs for solar energy production. It is envisioned that development of high efficiency and high heat capacity thermal storage fluids will reduce the overall thermal storage costs, increase system efficiency, reduce structural storage volume, and contribute to bringing solar power generation costs in line with other conventional power generation sources. Particularly, with respect to CSPs, current high temperature energy storage fluids such as molten salts are relatively limited in terms of their thermal energy storage capacity. There is therefore a critical need to develop advanced high temperature fluids (“HTFs”) and thermal storage systems to reduce the costs and improve efficiencies. Current HTFs, such as synthetic oils, have low thermal conductivity and limited thermal energy storage capacity. It has been demonstrated in recent years that addition of solid nanomaterials to various fluids can increase the thermal conductivity, density, and heat transfer coefficient of nanofluids by tens of percent.
Nanoparticles of functional materials, such as phase change materials (“PCM”), can contribute additional thermal energy storage capacity through the latent heat of solid/liquid or solid I/solid II transformations. Encapsulated in thermally stable and chemically inert shells, PCM nanomaterials dispersed in HTF nanofluids can increase volumetric thermal storage capacity. Studies of micron-sized encapsulated phase change materials have been conducted previously for low temperature heat transfer fluids. The micron sized PCM did not perform well under repeated cycling. The larger particles were often crushed during pumping, and the phase change of the PCMs was frequently incomplete due to the poor thermal conductivity. Consequently, there is a great need for developing articles and methods for storing energy collected by any means, such as for example, by solar energy methods.